Fire Barrier Wall = Separate Building?

Can a fire barrier wall constructed per NFPA 221 chapter 7 be used to separate attached occupancies in regards to when a fire sprinkler system is required throughout the building? For example there is an existing 2 family unsprinkled building that the owners are add a new dwelling unit addition to the building that will have its own separate means of egress. I believe this would make the building fall under NFPA 101 chapter 30 and per 30.3.5.1 all building shall be protected throughout by an approved automatic sprinkler system. My questions are as follows:

Does a 2 hour fire barrier separation between the new and existing units per NFPA 221 mean that the building could be looked at as a new single family unit requiring only a 13D sprinkler system and an existing 2 family the would not require a sprinkler system?

Would a fire wall per NFPA 221 chapter 6 be required consider the occupancies separate buildings?

Can a 2 hour fire barrier that was both horizontal and vertical be allowed to separate occupancies. For example can a new dwelling unit would be added to the top of an existing 2 family building bring the total number of units to 3. If there were a fire barrier separation between the new and the existing units including a separate egress stair. Could these be looked at as separate buildings or a new apartment building?

Does a 2 hour fire barrier separation between the new and existing units per NFPA 221 mean that the building could be looked at as a new single family unit requiring only a 13D sprinkler system and an existing 2 family the would not require a sprinkler system? NFPA 101 does not have provisions for separate buildings by a fire barrier. It does have a fire barrier as an option to separate differing construction types in a building. From the NFPA 101 perspective, if the occupancy chapter requires a automatic sprinkler system throughout the building, the fire barrier separation would not cause one section of the building to unsprinklered.

Would a fire wall per NFPA 221 chapter 6 be required consider the occupancies separate buildings? NFPA 5000 or the the International Building Code may have a legal means to separate buildings specifically when there is a lot line between the buildings. If this legal separation by the building codes can be documented, your AHJ may be convinced there are two legally separate buildings. Sometimes this takes a separate address for each building. In the NFPA 101 perspective, to be separate all means of egress for each building must be independent and no sharing any exit accesses. NFPA 101 is not a building code.

Can a 2 hour fire barrier that was both horizontal and vertical be allowed to separate occupancies. For example can a new dwelling unit would be added to the top of an existing 2 family building bring the total number of units to 3. If there were a fire barrier separation between the new and the existing units including a separate egress stair. Could these be looked at as separate buildings or a new apartment building? NFPA 101 has no occupancy separation provisions for a fire barrier to separate buildings. The entire building may be a new apartment occupancy. I suggest looking at NFPA 101 Chapter 43 for new addition to existing buildings. It will lead you on the requirements of new construction.